powerpc/pseries/pci: Code cleanup

This part was commented in about 19 years before.
If there are no plans to enable this part code in the future,
we can remove this dead code.

Signed-off-by: Kunwu Chan <chentao@kylinos.cn>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240126025030.577795-1-chentao@kylinos.cn